The present invention relates to an anesthesia breathing circuit and/or system which is useful in either a closed or a semi-closed anesthetic supply system and functions to simplify the overall system while at the same time introducing certain efficiencies and economies of manufacture.
Generally, in the practice in inhalation anesthesia administration, a system is frequently employed wherein a patient undergoing anesthesia rebreathes all or part of the exhaled gases. The inhaled and exhaled gases generally are contained in a circuit which is either closed or semi-closed, a closed circuit preventing any significant amount of gas to leave the circuit while a semi-closed system allows a portion of the gas to escape, usually into the atmosphere. In both systems, the exhalation gases, including carbon dioxide as well as the anesthetic gases are generally directed to a filter system which removes the carbon dioxide and then reintroduces the remaining gases along with additional new gases back into the inhalation portion of the system. In general, the circuit consists of the anesthesia machine, valving to establish unidirectional flow for the gases, a relief or pop-off valve, a carbon dioxide removal device, otherwise known as an absorber, a breathing bag, breathing tubes or conduits for carrying the gas to and from the patient, and a face mask or endotracheal tube.
With respect to those circuits presently known in the art, it is the common practice to employ a separate inhalation tube and a separate exhalation tube, which are each separately connected to the anesthesia machine, and also separately connected to the patient's face mask. By employing unidirectional valves, exhaled gases will mostly enter the exhalation tube, whereas inhaled gases will mostly enter through the inhalation tube, the unidirectional flow valves functioning to prevent the gases from intermixing between the two tube lines. For example, a recent U.S. Pat. No. 3,721,239 discloses an anesthetic gas exhaust system which shows a system of the general type discussed above, having both an inhalation line and an exhalation line connected to an anesthetic supply system at one end, and to the patient face mask at the opposed end. While many recent additions and modifications have been proposed, most of these improvements have dealt with the utilization of materials to allow a single patient disposable application for antiseptic purposes, however, major components of this system have not basically changed. As a result, the various drawbacks which are inherent in such circuits have remained and have merely been accommodated by the majority of the modifications and improvements made in the field.
Exemplary of such drawbacks is the two tubular system, presently employed. Generally, such anesthesia systems include an inhalation line, which interconnects between the anesthesia supply equipment and the patient's face mask, or other patient supported inhalation-exhalation means, and a separate exhalation tube which again interconnects between the patient's face mask or other such device, and some type of purification equipment such as a carbon dioxide absorber. The provision of a two tubular system presents many difficulties, including the accumulation of water within the tubing resulting from condensation from the gases passing through the tubing; the increased danger of bacterial growth in the tubing especially in the presence of accumulated water of condensation; the loss of heat from the gas as it travels down the inhalation line prior to inhalation by the patient; the requirement or necessity for taping or otherwise supporting the tubes, by taping the same to the patient, or the surgical table in order to support the tubes and minimize entanglements; and it is apparent that some degree of manipulative skill is necessary in order to properly connect the tubes. Another drawback, which has been incorporated into the present systems, relates to the location of the unidirectional flow valves at a point somewhat spaced from the patient, or the patient's face mask, that is at the anesthesia machine. The inherent disadvantage to this structure is the fact that there is created a great deal of space for exhaled gas to accumulate or to reside such that a portion thereof may be inhaled during the next inspiration. This results in the inhalation of gas with a higher than desirable concentration of carbon dioxide.